Linear actuators are conventionally used to controllably move a member between two or more positions. There are many applications for linear actuators, each application having different system requirements. There are many parameters that may need to be precisely controlled, such as positioning, distance, speed, force, and time just to name a few.
When multiple linear actuators are used in a system, the complexity of the system increases due to various attributes of the actuators. For example, the performance of an actuator often varies with temperature and age, and thus tolerances are established to allow integration of two or more actuators to cooperate and perform a function. In precise applications, feedback control is typically required to maintain performance of an actuator. Feedback is used to remove errors that can negatively affect the linearity of the system. When two or more linear actuators are coupled to a member, unbalanced forces can reduce the linearity of the system and degrade performance. Also, unbalanced forces can couple with dynamic modes of the driven object, compromising the integrity of in an example case, the reflected surface figure of a mirror.